Posted by Rick Denney on February 04, 2004 at 18:14:27:
In Reply to: Re: B&S History posted by A ? for you... on February 04, 2004 at 16:35:59:
I'd have to measure it.
A slightly larger pipe would only have the effect of slowing the air down a little. Air moving faster creates more friction which slows it down and creates more pressure. So, if the fifth valve branch is a little fatter, it would just reduce the friction, making it blow more openly.
A venturi is a narrowing, where the air speeds up. The venturi effect is the vacuum caused by this speeding up, which is used to draw fluid into the venturi (as with, say, a carburetor). It could affect resonance if it occurs at just the wrong place, I suppose.
The Holton's fourth valve branch is .810", though the valve ports are .750". The knuckles handle the transition. It slows the air down in the fourth-valve branch to reduce friction and make it more open-blowing. In my case, it almost makes it too open-blowing.
Mine has the typical design where the leadpipe enters the lower port on the fifth valve instead of coming in from the top as with, say, an Alexander. It makes for a shorter leadpipe, and the corner the air turns seems to be no big deal.
Rick "who will compare the slides this evening" Denney